Numerically controlled grinding machine with a sizing device

ABSTRACT

A grinding machine is provided with a sizing device for providing a sizing signal which controls a hydraulic actuator to feed a wheel slide. A sizing point of the sizing signal is shifted to be preset in accordance with numerical information of a desired finish dimension of a workpiece before grinding. In accordance with the numerical information, simultaneously it is compensated in an original position of the wheel slide relative to the workpiece by a servomotor so that the vacant space between a grinding wheel and the workpiece may be maintained constant when the grinding wheel has been advanced by its hydraulic actuator to the rapid feed end of its feed stroke.

United States Patent NUMERICALLY CONTROLLED GRINDING MACHINE WITH ASIZING DEVICE 6 Claims, 8 Drawing Figs.

U.S.Cl 51/165 R, 51/165 TP. 5 l/l65.8

Int. Cl B24b 49/04 Field of Search 51/165 R,

I F E y 11111111111 h [56] References Cited UNITED STATES PATENTS2,509,368 5/1950 Price 51/1659 x 3,056,240 10/1962 Morgan et 31.. 51/165TP 3.l92,675 7/1965 Fries et al. 51/165 R 3,568,372 3/1971 AS21110 etal. 51/165 R Primary E.\'aminer Lester M. Swingle Attorney-Herman.Davidson and Herman ABSTRACT: A grinding machine is provided with asizing device for providing a sizing signal which controls a hydraulicactuator to feed a wheel slide. A sizing point of the sizing signal isshifted to be preset in accordance with numerical information ofadesired finish dimension ofa workpiece before grinding. In accordancewith the numerical information.

simultaneously it is compensated in an original position of the wheelslide relative to the workpiece by a servomotor so that the vacant spacebetween a grinding wheel and the workpiece may be maintained constantwhen the grinding wheel has been advanced by its hydraulic actuator tothe rapid feed end of its feed stroke.

PAIENTEUNUV 23 IQTI SHEET 1 UF 5 mfwww Q Q @N NM MM mm NXMQYMNMS Q Y a 5M N r 2 6 .0 MET 7 a? T M ,f A W W 1R4 w BACKGROUND OF THE INVENTION Thepresent invention relates to a grinding machine and more particularly toan apparatus for controlling the transverse movement of a grinding wheelin accordance with numerical information of a finish dimension of aworkpiece.

Grinding machines employing numerical control systems are becoming moreprevalent in accordance with the spread of numerical control systemsgenerally with regard to machine tools. Generally speaking, however, ithas been difiicult to adopt numerical control systems in the art ofprecision grinding operations in which micron order of accuracy isrequired, in contrast to the lesser degree of required accuracy withcutting operations. In fact, it is not easy to accurately position theperipheral surface of a grinding wheel relative to that of a workpiecefor reasons such as thermal deformations of the grinding machine and theworkpiece, backlash of the feed screw in e prfeeding mechanism, grindingwheel wear, and the like. Therefore, high precision in a grindingoperation cannot be expected wherein the feed movement of the wheelslide is controlled only by a numerical control device for the feedscrew of the wheel slide.

For the purpose of overcoming the aforementioned disadvantages, it hasbeen proposed that the grinding machine use a numerical control devicetogether with a sizing device which measures directly a diameter of theworkpiece to be worked on to provide a sizing signal, wherein the sizingpoint is preset by changing the space between a pair of measuringfeelers in accordance with numerical information of a finish di ameter.However, the sizing device can but control the feed movement during agrinding operation, so that other information is required to controlfeed speed change from a rapid feed rate to a slow feed rate forgrinding and the feed amount in the transverse movement of the wheelslide.

Accordingly, a plurality of sets of information, such as mentionedabove, must ogrammed and encoded on a tape or record for the purpose ofachieving the feed control of the wheel slide. As a result, theprogramming for a machining operation has been considerably bulky andcomplicated, whereas the conventional system has been satisfactory inmany other respects.

It is. therefore, desirable to control precisely the transverse movementof the wheel slide over a wide range only by numerical informationrelative to the desired finish diameter of the workpiece through theagency ofa sizing device.

SUMMARY OF THE INVENTION According to the present invention, there isprovided a grinding machine which comprises feed means for moving a feedscrew threadedly engaging with a wheel slide to move the same,compensating means having a first servornotor for compensating anoriginal position of the wheel slide relative to a workpiece inaccordance with a command, sizing means for providing a sizing signal tocontrol the feed means in response to the diameter of the workpieceduring a grinding operation, the sizing signal being generated at apredetermined sizing point, which is shifted to be preset by changing aspace between a pair of measuring feelers of the sizing means throughthe agency of a second servornotor of the sizing means in accordancewith the command before the grinding operation, and control means forsimultaneously providing the command to the first and second servomotorsto cause them to operate in accordance with numerical information of adesired finish dimension ofthe workpiece.

The first and the second servomotors are simultaneously operated inaccordance with the same command for the grinding operation. Thecompensating operation ofthe wheel slide, whose amount is equal to equalto one-half of the differential in a desired finish diameter between theworkpiece and the workpiece previously worked, is simultaneouslyperformed together with the shifting operation of the sizing point,through the feed means.

After the aforementioned operation, the wheel slide is advanced by thefeed means toward the workpiece at 'a rapid feed rate, which is shiftedto a reduced rate for grinding just before t he grin din g wheel comesinto contact with the work piece. The feed operation thereafter iscontrolled by m2 sizing w '7 I signal from the sizing means.

An object of the invention is to provide a grinding machine with asimplified and inexpensive control system in which it is easy to programa feed operation of the wheel slide. Another object of the invention isto provide a grinding machine with compensating means for compensatingan original position of the wheel slide relative to a workpiece inaccordance with numerical information of a desired finish dimension ofthe workpiece.

Another object of the invention is to provide a grinding machine withsizing means for providing a sizing signal to control the movement ofthe wheel slide, the sizing signal being generated at a predetenninedsizing point, which is shifted by a servomotor in accordance withnumerical information of a desired finish dimension of a workpiece.

Another object of the invention is to provide a grinding machine withcontrol means which provides a command corresponding with numericalinformation of a desired finish dimension simultaneously to compensatingmeans for the wheel slide and to sizing means.

DESCRIPTION OF THE DRAWINGS The foregoing and other objects of thepresent invention will become fully apparent from the followingdescription of a preferred embodiment of the present invention withreference to the accompanying drawings, in which:

FIG. 1 is a transverse sectional view mechanism for a wheel slide.

FIG. 2 is a sectional view taken along the line 22 of FIG.

showing a feed FIG. 3 is a sectional view taken along the line 3-3 ofFIG. 1.

FIG. 4 is a longitudinal sectional view showing a sizing device on alarge scale.

FIG. 5 is a sectional view taken along the line 55 of FIG. 4.

FIG. 6 is a sectional view taken along the line 66 of FIG. 4.

FIG. 7 is a block diagram showing the control system of the sizingdevice and the feed mechanism for the wheel slide.

FIG. 8 is a wiring diagram of the hydraulic control circuit employed inthe system shown in FIG. 7.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGS. 1 to 3 showinga feed mechanism of a grinding machine, a bed 10 fixedly mounts thereona wheel base 11 which slidably receives a wheel slide 12 thereon formovement in one direction along guideways l3 and 14, shown in FIG. 3,formed on the wheel base 1 l. A grinding wheel 15 is rotatably carriedin the wheel slide 12 and is actuated by an electric motor 16 secured onthe wheel slide 12. The wheel base II has thereon two opposite hubportions 17 and 18 which slidably and rotatively receive a feed screw 19therein. The hub portion 18 includes a hydraulic actuator 20, for arapid feed movement of the wheel slide 12, consisting of a cylindricalbore 21, a piston 22 slidably received in the bore 21 and a piston rod23 defined by one end of the feed screw 19 and connected to the piston22. The threaded portion of the feed screw engages a nut sleeve 24rotatably mounted by bearings 25 and 26 in a bracket 27 which is securedon the lower surface of the wheel slide 12.

The threaded portion of the feed screw 19 also engages a female screwmember 28 adjacent to the nut sleeve 24 and slidably received in abracket 29 secured on the lower surface of the wheel slide 12. Thefemale screw member 28 is normally urged toward the nut sleeve 24 by theforce of pressure fluid supplied in a chamber 30 defined by the femalemember 28 and the bracket 29, with engagement ofa radial groove 31 atone end of the female member 28 with a projection 32 at one end of thenut sleeve 24, whereby to eliminate backlash between the feed screw 19and the nut sleeve 24.

A worm wheel 35 keyed to the nut sleeve 24 engages with a worm 36 keyedto one end ofa shaft 37 rotatably joumaled in the wheel slide 12, asshown in FIG. 3.

A gear 38 secured to the other end of the shaft 37 meshingly engageswith a gear 39 secured to the output shaft 40 of a pulse motor 41fixedly mounted on the wheel slide 12. Thus, the worm wheel 35, and inturn, the nut sleeve 24 are rotated by the pulse motor 41 through thegear train. When the pulse motor 41 is inoperative, the nut sleeve 24 isrestrained against rotation through the worm interengagement.

On the rearward portion of the feedshaft 19 is formed a gear 42 which isin slidable meshing engagement with a relatively long gear 43. The gear43 is meshingly engaged with a gear 44 secured on the right end portionof a driving shaft 45 which is rotatably mounted in the bed 10.

As shown in FIG. 2, a manually operable hand wheel 46 is secured on theleft end ofa shaft 47 rotatably supported in the bed 10, and a gear 48formed on the shaft 47 is meshingly engaged with a gear 49concentrically secured on the driving shaft 45 through a clutch member50. On the bed is mounted a hydraulic actuator 51, for slow feedmovement of the wheel slide 12, including a piston rod 52 on which arack 53 is formed. The rack 53 is engaged with a gear 54 rotatablymounted on a shaft 55 which is fixedly secured to the bed 10. The gear54 is, in turn, engaged with a gear 56 formed on a sleeve 57 which isrotatably supported in a bore formed in the bedv The sleeve 57 rotatablysupports therein a reduced portion 58 of the driving shaft 45. A clutchcylinder 59 is connected to the right end of the sleeve 57. A clutchpiston 60 is slidably keyed internally to the clutch cylinder 59 and ismovably mounted on the reduced portion 58 of the driving shaft 45. Thepiston 60 is rightwardly movable by operation of pressure fluid so thatan inner conical surface 61 formed on the piston 60 may becomplementally and frictionally engaged with an outer conical surface 62of the clutch member 50. A spring 63 is seated between the clutchelements 60 and 50 to release engagement therebetween.

in operation, the feed screw 19 may be rotated through the driving shaft45 and the gears 44, 43 and 42 either manually by the hand wheel 46 withthe above-described clutch means disengaged, or automatically by theslow feed hydraulic actuator 51 with said clutch means engaged.Moreover. the feed screw 19 may be rapidly moved in its axial directionby the rapid hydraulic actuator 20. Rotatably mounted in the hub portion17 of the wheel base 11 is a stop member 64 which is adapted to beengaged with the left end of the feed screw 19 upon rapid movement ofthe wheel slide 12 to the left by the actuator 20.

At the right end of the drive shaft 45 is provided an automatic grindingwheel compensating apparatus 65 which comprises a ratchet mechanism 66and a hydraulic actuator 67. The operation of hydraulic actuator 67causes the feed screw 19 to be rotated through the ratchet mechanism 66and the gearing so that the wheel slide 12 is advanced to the left by acompensating amount equal to a dressing amount by which the periphery ofthe grinding wheel is dressed by a dressing apparatus (not shown).

A worktable 70 is slidably mounted for movement in a directionperpendicular to the direction of the wheel slide 12 on guideways 71,72, 73 and 74 through way bearings 75, 76, 77 and 78. The worktable 70is adapted to be driven by a suitable actuator (not shown) to positionthe work with respect to the grinding wheel in various work operationpositions. On the worktable 70 is pivotally mounted a swivel table 79 onwhich a headstock 30 and a tailstock (not shown) are mounted in awell-known manner, and a workpiece W is supported therebetween. A sizingdevice 81 for sizing or measuring the diameter of the workpiece W isconnected to one end of a piston rod 82. the other end of which isconnected to a piston 83, slidably mounted in a hydraulic actuator 84.The

hydraulic actuator 84 is fixed on a base member 85 secured to the bed 10through a pedestal 86. The base member 85 has therein a slidable guiderod 87, one end of which is connected to the sizing device 81 forguidance thereof. The operation of the hydraulic actuator 84 moves thesizing device 81 toward and away from the sizing position where thefeelers 115, 116 embrace the workpiece W at diametrically oppositeportions.

As best shown in FIG. 4, the sizing device 81 comprises a sizing headpivotally mounted by a pin 91 on a bracket 92 connected to the guide rod87 and the piston rod 82 of the hydraulic actuator 84. At the lower endof the sizing head 90 is mounted a plunger 93 which is urged by a spring94 toward the front surface of bracket 92 so as to maintain the sizinghead balance around the pivot pin 91. A projection 95 adjustably securedto the sizing head 90 and having an enlarged portion at its left endregulates the range of pivotal movement of the sizing head 90,cooperating with a stop 96 fixed on the bracket 92.

On the upper and lower ends of the sizing head 90 are respectivelysecured jaws 97 and 98 which mount two guide bars 99 and 100therebetween, and opposite ends of the guide bars 99 and 100 are securedby nuts 117 and 118 to the jaws 97 and 98. On an axis equidistant fromthe axes of guide bars 99 and 100 is rotatably mounted a feed rod 101 onwhich a right-hand threaded portion 102 and a left-hand threaded portion103 are formed. On the upper portion of the feed rod 101 is secured agear 104 which is drivingly coupled with the output shaft ofa pulsemotor 111 mounted on the sizing head 90 through gears 105, 106, 107, 108and 109. The compound gears 104, 106 and 108 which each comprise twoconcentric relatively rotatable gears urged by a spring 112 therebetweenare meshingly engaged with single gears 105, 107 and 109, respectively.so as to eliminate backlash of the gears. Movable support members 113and 114 carrying measuring feelers 115 and 116 thereon respectively areslidably mounted on guide bars 99 and 100. The support members 113 and114 are formed with openings for the guide bars 99 and 100 and the feedrod 101 extending therethrough.

A downwardly directed cylindrical extension 120 is formed integrallywith the support member 113, and a pair of guide bushings 121a and 12112are fitted in the upper end and the lower end respectively of the bore123 of the support member 113 and the cylindrical extension 120. Anupwardly directed cylindrical extension 124 is formed integrally withthe support member 114, and a pair of guide bushings 125a and 12512 arefitted in the upper and the lower ends respectively of the bore 127 ofthe support member 114 and the cylindrical extension 124. The openings128 and 129 formed in the support members 113 and 114 respectively forthe feed rod 101 extending therethrough have secured therein femalethreaded members 130 and 131 which threadedly engage the right-handthreaded member 102 and the left-hand threaded member 103 of the feedrod respectively. Each of the internally threaded members 130 and 131consists ofa set of two nuts of the circulating ball-type. The two nutsare rendered preloaded through adjustment of the thickness of a spacingcollar interposed therebetween to eliminate backlash of the threadedportions.

The feeler 115 is adjustably mounted by a dovetail engagement on theupper support member 113, while a block 132 pivotally mounting thefeeler 116 and including a built-in displacement detector 133 such as adifferential transformer, to detect the displacement of the pivotalfeeler 116, is adjustably mounted by dovetail engagement on the lowersupport member 114. Upon predetermined pivotal movement of the feeler116, the detector initiates a sizing signal at a sizing point, which isset by changing the space between the pair of measuring feelers, wherebyto change the feed rate of the grinding wheel.

A bellows 134 made of rubber or like material is clamped at its lowerend to the periphery of the upper end of the support member 113 and atits upper end to the peripheral edge of the jaw 97. Similarly, a bellows135 is clamped at its opposite ends to the periphery of the lower end ofthe support member 114 and the peripheral edge of the jaw 98, A bellows137 is clamped at its opposite ends to the lower end of the supportmember 113 and the upper end of the support member 114. The provision ofbellows 134, 135 and 137 is effective to prevent grinding wheel granulesand coolant from adhering to the guide rods and the feed rod by coveringand enclosing same.

As described above, thesizing device 81 is effective to rotate the feedrod 101 through the associated gearing upon application of predeterminedpulse signals through the pulse motor 111, thereby to accurately movethe support member 113 and the support member 114 having thereon thefeelers 115 and 116, respectively, by a predetermined amount indirections opposite to each other. Since the displacement detector 133is moved together with the feeler 116, the sizing point is shifted inaccordance with the change of the interval between the feelers 115 and116. Control of the pulse signals to the pulse motor 111 in accordancewith change in diameter of the workpiece to be ground enables automaticsizing of a plurality of workpieces with different diameters, or oneworkpiece with a plurality of stepped portions, by the same sizingdevice 81. This automatic sizing permits a sizing signal to be generatedat the sizing point, providing a predetermined voltage level of thedisplacement detector 133, to control the feed rate of the wheel slide12.

A numerical control circuit for controlling the aforementioned deviceswill be described hereinafter with reference to FIG.7 Numeral 140 refersto a tape reader, 141 to a decoder, 142 to a preset counter, 143 to apulse generator, 144 to a gate, 145 to a control circuit, 146 and 147 todrive circuits for the pulse motors 111 and 41, 148 to a manualoperations circuit, 149 through 152 to AND gates, the aforementioneddevices being well known and commercially available, and 153 to ahydraulic control circuit for feed movement of the wheel slide 12. Thehydraulic control circuit 153 is adapted to control energization anddeenergization of solenoids 154, 155 and 156 of solenoid valves 157, 158and 159 which are connected to the hydraulic actuators 20 and 51 so asto change the feed rate of the wheel slide 12, as described hereinafter.

In FIG. 8, a switch SW is closed by a command transmitted from themanual operation circuit 148 through the control circuit 145 to energizerelay 1CR of line 1. At the same time, normally open contacts lCRl and1CR2 are closed to energize solenoid 154, energizing solenoid 155 and156 through normally closed contacts 2CR1 and 3CR1.

Upon energization of solenoids 154, 155 and 156, the solenoid valve 157is reversed and the valves 158 and 159 are opened so that fluid underpressure is supplied from a fluid supply source (not shown) into eachone of the chambers of the actuators 20 and 51, thereby to advance thewheel slide 12 toward the workpiece W at a rapid feed rate by themovement of pistons 22 and 52. Thereafter, upon engagement of the leftend of feed screw 19 with the stop member 64, the wheel slide member 12is advanced at a reduced speed by the movement of piston 52 for roughgrinding. The reduced speed is determined by the orifice size of a flowcontrol valve 160 interposed between the actuator 51 and the solenoidvalve 158.

When the rough grinding operation has been performed, relay 2CR of line3 is energized by a first pulse signal from Schmidt circuit 167, asdescribed hereinafter, to open normally closed contacts 2CR1 whereby thesolenoid 155 is deenergized to shut a bypass passage including the valve158 so that the wheel slide 12 is advanced at a further reduced speedfor fine grinding, which is determined by the setting ofa flow controlvalve 161. When a fine grinding operation has been performed, relay 3CRand timer TR are energized by a second pulse signal from the Schmidtcircuit 167 to open normally closed contacts 3CR, deenergizing solenoid156. Upon the deenergization of solenoid 156, the solenoid valve 159 isclosed to block the exhaust flow from the actuator 51. Thus, thegrinding wheel remains stopped at the grinding position of the workpieceW to effect a spark-out operation, of which the time duration is presetby the timer relay TR.

The timer relay is deenergized after a predetermined time to open timerswitch TR, deenergizing relay 1CR, whereby normally open contacts 1CRlland 1CR2 are opened to deenergize solenoid 154. Upon deenergization ofsolenoid 154 after the spark-out operation, the solenoid valve 157 ischanged over to the position shown in H6. 7, to return the wheel slide.12 and the pistons 22 and 52 to their original positions shown in F|G.7,at a rapid speed. Upon retraction of wheel slide 12 to its originalposition, the hydraulic control circuit 153 operates the control circuit145 to perform the succeeding grinding operation.

The displacement detector 133 in the sizing device 81 is connected tothe hydraulic control circuit 153 through an amplifier 165, a rectifiercircuit 166 and a Schmidt trigger circuit 167 which compares an outputsignal of the detector 133 with preset voltage thereof. A pulse signalis generated at the sizing point, that is, when the output signalvoltage level of the detector 133 is over the preset voltage level inthe Schmidt circuit 167. This pulse signal is transmitted to thehydraulic control circuit 153 to actuate the solenoid valves 157, 158and 159, thereby to control the feed rate of the wheel slide 12 for finegrinding operation, spark-out operation and the rapid return of thewheel slide 12.

The drive circuit 147 is connected so as to control the pulse motor 41which rotates the nut sleeve 24 with respect to the feed screw 19through the associated gearing, whereby the wheel slide 12 is relativelymoved in response to pulses applied by the pulse generator 143 to thedrive circuit 147 through the gate 144. The drive circuit 146 isconnected to the pulse motor 111 of the sizing device 81 to rotate thethreaded rod 101 through a predetermined angle whereby the feeler andthe feeler 116, including the detector 133, are moved in accordance withthe numerical information relative to a desired finish dimension of theworkpiece W. Thus, the sizing point of the sizing signal is shifted tobe preset by changing the space between the pair of feelers 115 and 116in accordance with the desired finish diameter.

Opening and closing of the AND gates 149 through 152 are controlled by acommand from the control circuit 145. When opened by the control circuitthrough a line 170, the AND gates 149 and 151 pennit the output pulsesfrom the pulse generator 143 to be applied to the drive circuits 146 and147 to simultaneously rotate the pulse motors 111 and 141 apredetermined angular amount in one direction. On the other hand, whenopened by the control circuit 145 through a line 171, the AND gates and152 permit the output pulses from the pulse generator 143 to be appliedto the drive circuits 146 and 147 to simultaneously rotate the pulsemotors 111 and 41 a predetermined angular amount in the oppositedirection.

Thus, the wheel slide 11 is automatically moved and compensated inaccordance with the displacement amount of the feelers 115 and 116 ofthe sizing device 81, that is, the wheel slide 12 is transversely movedby cooperation of the nut sleeve 24 and the feed screw 19 to compensatethe position of the grinding wheel 15 relative to the workpiece W by anamount corresponding to change in diameter of the workpiece so that whenthe left end of the feed screw 19 is engaged with the stop member 64 thegrinding wheel is located at a shifted position in accordance with thechange in radius of the workpiece.

Thus, the rapid feed speed may be changed to the reduced feed speed forrough grinding just before the grinding wheel 15 is brought into contactwith the workpiece without regard to the change in diameter of theworkpiece.

in addition, it will be seen that when grinding depth of cut is changed,the change thereof has to be programmed and a compensation pulse isapplied only to the pulse motor 41 in accordance with a programmedcommand value.

In this way, the position of the wheel support 12 may be recompensatedin accordance with the change in the grinding allowance so as to keepvacant or idle grinding time to a minimum.

The operation necessary to automatically grind workpieces of differentdiameters and the control means for grinding operation will be describedhereinafter.

lnitial master setting of the sizing point corresponding to a referencediameter is performed in a manner whereby a reference master gaugehaving the reference diameter is supported between the centers of theheadstock and the tailstock, and thereafter the sizing device isadvanced toward the reference master gauge and is positioned at thesizing location. In turn, the manual operation circuit 148 is operatedto cause a manual pulse generator (not shown) to apply the requirednumber of pulses to the drive circuit 146, whereby the pulse motor 111is actuated to regulate the space between feelers 115 and 116 inaccordance with the reference diameter, namely, until the sizing signalis generated at the sizing point, or the predetermined voltage level ofthe displacement detector 133 is attained. As soon as the sizing signalis generated, the aforementioned pulse supply is stopped, whereby to setup the sizing point corresponding to the reference diameter of thereference master gauge. Thereafter, with the clutch member 60 disengagedfrom the clutch member 50, the wheel slide 12 is advanced by theactuator 20 to the terminal position of rapid feed movement. In thereleased condition of the clutch, the power feed by actuator 51 is noteffective, whereas the drive shaft 45 may be manually rotated by thehandwheel 46 through the associated gearing. Thus, the wheel slide 12 isadvanced by the handwheel 46 to regulate the rapid feed stroke endthereof relative to the workpiece, so that a vacant space required fordiversity in diameter of the workpiece and for grinding allowance may beformed between the peripheral surfaces of the reference master gauge andthe grinding wheel 15. In turn, the piston 22 in the actuator 20 isreturned to its original position and the clutch elements 50 and 60 arefrictionally interengaged by admitting pressure fluid into the clutchcylinder 59.

As to the first command on the program relative to the transversemovement of the wheel slide 12, a differential in the desired finishradius between the reference master gauge and a workpiece to be workedis encoded on the tape, together with plus or minus sign data describedhereunder. As to a second command, a differential in the desired finishradius between the first workpiece and a workpiece to be subsequentlyworked is encoded on the tape together with plus or minus sign data.

As to a third command, similarly, a differential in dimension betweenthe second and a third workpiece is coded on the tape together with plusor minus sign data. Thus, on the tape or record is encoded the machininginformation which includes the differential in finish dimension betweenthe preceding and the following workpieces to be worked and plus orminus sign data.

In addition, it can be seen that if a calculative function is added tothe control device, the desired finish radius of each workpiece can bedirectly encoded on the tape without the necessity of calculating thedifferential in dimension between the preceding and the followingworkpieces.

Moreover, the control circuit 145 is operated to provide an automaticoperation in which the tape reader 140 is caused to read the firstinformation which is registered in the preset counter 142. When the gate144 is opened, one of output lines 170 or 171 is selectively energizedin accordance with the direction information (plus or minus) on the tapethrough the control circuit 145. Assume a case wherein the value of themaster gauge is 20 millimeters in diameter and the value of the firstworkpiece is 30 millimeters, the word 5,000 (assuming 1 micron per eachpulse) corresponding to the differential millimeters in radiustherebetween, is preset in the preset counter 142. Then, the gates 149and 151 are simultaneously opened in accordance with the plus sign data,since the first workpiece is larger than the master gauge in diameter.Output pulses from the pulse generator 143 are applied to the drivecircuits 146 and 147 through the gate 144, the gates 149 and 151, andare simultaneously applied to the preset counter 152 to subtract onepulse from the registered or preset number of pulses each time thepreset counter 142 has received one pulse through the gate 144, which iseventually closed to stop pulses from going into the drive circuits whenthe number registered in the preset counter 142 has become zero.Accordingly, the predetermined number of pulses, corresponding to theregistered number is applied to the drive circuits 146 and 147 by meansof which the pulse motors 41 and 111 are simultaneously actuated toincrease the sizing distance by an amount corresponding to the firstinformation, or 5 millimeters in radius l0 millimeters between the pairof measuring feelers) and to move the wheel slide 12 rearwardly 5millimeters. Thus, the compensating operations of the sizing point andof the original position of wheel slide 12 are performed at the sametime. The hydraulic control circuit 153 is operated to advance the wheelslide 12 toward the workpiece at the rapid speed. Since the amount of 5millimeters in the position of wheel slide 12 has already beencompensated with reference to the terminal end of the rapid feed, asdescribed above, the grinding wheel surface is rapidly moved to theposition just before contacting the workpiece regardless of theworkpiece diameter, and in turn is advanced to the first workpiece at areduced speed for rough grinding. As the rough grinding operationprogresses, the workpiece to be worked on is reduced in diameter to avalue slightly greater than the finish dimension and the voltage fromthe detector approaches the operation point, or the predeterminedvoltage level. When the grinding operation has progressed to a pointwhere only the finish depth of cut is left on the workpiece, the firstsizing signal is generated by the action of Schmidt circuit 167 whichreceives the voltage from the detector 133 and causes the hydrauliccontrol circuit 153 to close the changeover valve 158 to change from thefirst reduced speed for rough grinding to the further reduced speed forfine grinding. Further progress in the grinding operation eventuallyresults in the generation of the second sizing signal, by which thevalve 159 is shut, as shown in FIG. 7, to stop the feed movement of thewheel slide 12, which is then moved rearwardly at rapid speed afterspark-out for a predetermined time defined by a timer (see FIG. 8). Thewheel slide 12 is returned to the starting position.

Similarly, a second command is read by the tape reader as to the finishradius of a workpiece to be second-worked, to automatically compensatethe sizing points and the original position in accordance with thesecond command, and thereafter the wheel slide 12 is moved toward thesecond workpiece by the hydraulic feed actuators. The feed movement ofthe wheel slide is controlled by the sizing signals of the sizing device81, as well as by the first operation.

in addition to the aforementioned operation, the grinding wheel 15 isdressed at an adequate time and the position of the wheel slide 12 iscompensated by the grinding wheel compensating apparatus 65 consistingof the conventional ratchet feed mechanism 66, the gearing and thehydraulic actuator 67, so as to maintain the grinding surface in aconstant position relative to the workpiece, since the displacementamount of the wheel slide 12 is equalized in accordance with thedressing amount. The compensating operation is performed in a wellknownmanner such that the hydraulic actuator 67 is operated in relation tothe dressing operation so as to rotate drive shaft 45 and the feed shaft19 through the action of the associated gearing and the engagementbetween a pawl and a ratchet under conditions of disengagement of theclutch members 50 and 60.

in the aforementioned compensating operation, it can be seen thatcompensating apparatus 65 may be omitted if an apparatus is added whichapplies a predetermined number of compensation pulses to the pulse motor41 in accordance with a directing signal.

Thus, since the feed movement of wheel slide 12 is controlled by sizingdevice 81, errors produced by thermal deformations of the grindingmachine and the workpiece and by grinding wheel wear and the like, arealmost excluded.

Moreover, it is possible to continuously measure either the diameters ofdifierent workpieces or the specified diameters of a multidiameterworkpiece.

In the present invention, since the compensating operations, which shiftthe generation point of sizing device 31 and regulate the originalposition of wheel slide 12 relative to the workpiece, are simultaneouslyperfonned by a common programmed command, it is easy to program themachining operation and to prevent making a mistake in the programming.Furthermore, the compensating operation corresponding to numericalinformation is performed at a time before starting of the grindingoperation. Thereafter, the predetermined infeed movement is performed bythe hydraulic actuators without regard to the numerical control deviceand is controlled by the sizing device in response to the diameter ofthe workpiece to be worked on. Therefore, according to the presentinvention, a simplified and inexpensive control device can be used as anumerical control system.

The various parts shown in the blocks in FIG. 7 are conventional, andmay be as follows:

Pulse motor 111: Model No. EPM-109 Pulse motor 41: Model No. EHPM-k-SSSS140-152 inclusive: Modules contained System, Model No. FAN UC 260.

The above items are manufactured by Fujitsu Ltd., Tokyo, Japan.

Schmidt circuit 167: Contained in Delta Model E-MD-P35 C-ZP manufacturedby Tokyo Seimitsu Ltd., Tokyo, Japan.

What is claimed is:

l. A grinding machine comprising a bed, a wheel slide slidably mountedon said bed, a grinding wheel rotatably supported on said wheel slide, atable mounted on said bed operably to support a workpiece, a feed screwmovably mounted on said bed and threadedly engaging with said wheelslide to move same, feed means drivingly engaging with said feed screw,compensating means having a first servomotor operatively mounted forcompensating an original position of said wheel slide relative to saidworkpiece in accordance with a command, sizing means providing a sizingsignal to control said feed means responsive to the diameter of saidworkpiece during a grinding operation, said sizing signal beinggenerated at a predetermined sizing point, means including a secondservomotor to shift said sizing point in accordance with said commandbefore said grinding operation, and control means simultaneouslyproviding said command to said first and second servomotors to causesame to operate in accordance with numerical information associated witha desired finish diameter of said workpiece.

2. A grinding machine as claimed in claim 1 in which said compensatingmeans comprises a nut member rotatably mounted on said wheel slide andengaging with said feed screw, a worm wheel coaxially secured to saidnut member, and a worm drivingly engaging with said wonn wheel androtated by said first servomotor on said wheel slide, and means wherebysaid nut member is rotated by said first servomotor to compensate saidoriginal position of said wheel slide by an amount equal to one-half ofthe differential in a desired finish diameter between said workpiece anda workpiece previously worked and is restrained against rotation whensaid first servomotor is inoperative.

3. A grinding machine as claimed in claim 1 in which the sizing meanscomprises a sizing head mounting two vertical guide bars fixedly securedthereto at their upper and lower ends, a threaded rod rotatably mountedon said sizing head in parallel relation to said guide bars anddrivingly engaged with said second servomotor, a pair of feelersslidably mounted on said guide bars and drivingly engaging with saidthreaded rod, said pair of feelers being maintained in contact with saidworkpiece at positions on said workpiece diametrically opposed to eachother during said grinding operation, and means whereby in FANUC thespace between said two feelers is shifted by an amount equal to thedifferential in a desired finish diameter between said workpiece and aworkpiece previously worked before said grindin operation.

4. A grin ing machine as claimed in claim 1 in which said control meanscomprises drive circuit means connected to both of said first and secondservomotors to drive the same, a gate connected to said drive circuitfor permitting a predetermined number of pulses corresponding to saidnumerical information to pass therethrough, and a pulse generator forproviding a train of pulses to said drive circuit means to said gate,whereby said first and second servomotors may be controlledsimultaneously by said numerical information.

5. A grinding machine as claimed in claim 4 in which said drive circuitmeans comprises a first drive circuit connected to said firstservomotor, a first pair of AND gates connected to said first drivecircuit and said first-named gate for controlling flow of said pulsesfrom said first-named gate to said first drive circuit to select arotational direction of said first servomotor in accordance with saidnumerical information, a second drive circuit connected to said secondservomotor, and a second pair of AND gates connected to said secondservomotor and said first-named gate for controlling flow of said pulsesfrom said first-named gate to said second drive circuit to select arotational direction of said second servomotor, whereby said first andsecond servomotors may be simultaneously rotated in the same direction.

6. A grinding machine comprising a bed, a wheel slide slidably mountedon said bed, a grinding wheel rotatably supported on said wheel slide, atable mounted on said bed operably to support a workpiece, a feed screwmovably mounted on said bed and threadedly engaging with said wheelslide to move same, feed means drivingly engaging with said feed screw,a first pulse motor mounted on said wheel slide, a worm secured to theoutput shaft of said first pulse motor, a nut member rotatably mountedon said wheel slide and engag ing with said feed screw, a worm wheelcoaxially secured to said nut member and engaging with said worm, asizing head mounting two vertical guide bars fixedly secured thereto attheir upper and lower ends, a second pulse motor mounted on said sizinghead, a threaded rod rotatably mounted on said sizing head in parallelrelation to said guide bars and drivingly engaged with said second pulsemotor, a pair of feelers slidably mounted on said guide bars anddrivingly engaged with said threaded rod, said pair of feelers beingmaintained in contact with said workpiece at positions on said workpiecediametrically opposed to each other during a grinding operation, adetector mounted on one of said feelers for providing a sizing signal tocontrol said feed means during said grinding operation, a first drivecircuit connected to said first pulse motor to drive the same, a firstpair of AND gates connected to said first drive circuit for controllingflow of pulses into said first drive circuit to select a rotationaldirection of said first pulse motor in accordance with numericalinformation, a second drive circuit connected to said second pulse motorto drive the same, a second pair of AND gates connected to said seconddrive circuit for controlling flow of pulses into said second drivecircuit to select a rotational direction of said second pulse motor inaccordance with said numerical information, a gate connected to saidfirst and second pair of AND gates and permitting a predetermined numberof pulses corresponding to numerical information to pass therethrough,said numerical information corresponding to the differential in adesired finish diameter between said workpiece and a workpiecepreviously worked, and pulse generator means providing a train of pulsesto said first and second pair of AND gates through said last-named gate,whereby said first and second pulse motors may be simultaneously rotatedin accordance with said numerical infonnation.

2. A grinding machine as claimed in claim 1 in which said compensatingmeans comprises a nut member rotatably mounted on said wheel slide andengaging with said feed screw, a worm wheel coaxially secured to saidnut member, and a worm drivingly engaging with said worm wheel androtated by said first servomotor on said wheel slide, and means wherebysaid nut member is rotated by said first servo motor to compensate saidoriginal position of said wheel slide by an amount equal to one-half ofthe differential in a desired finish diameter between said workpiece anda workpiece previously worked and is restrained against rotation whensaid first servomotor is inoperative.
 3. A grinding machine as claimedin claim 1 in which the sizing means comprises a sizing head mountingtwo vertical guide bars fixedly secured thereto at their upper and lowerends, a threaded rod rotatably mounted on said sizing head in parallelrelation to said guide bars and drivingly engaged with said secondservomotor, a pair of feelers slidably mounted on said guide bars anddrivingly engaging with said threaded rod, said pair of feelers beingmaintained in contact with said workpiece at positions on said workpiecediametrically opposed to each other during said grinding operation, andmeans whereby the space between said two feelers is shifted by an amountequal to the differential in a desired finish diameter between saidworkpiece and a workpiece previously worked before said grindingoperation.
 4. A grinding machine as claimed in claim 1 in which saidcontrol means comprises drive circuit means connected to both of saidfirst and second servomotors to drive the same, a gate connected to saiddrive circuit for permitting a predetermined number of pulsescorresponding to said numerical information to pass therethrough, and apulse generator for providing a train of pulses to said drive circuitmeans to said gate, whereby said first and second servomotors may becontrolled simultaneously by said numerical information.
 5. A grindingmachine as claimed in claim 4 in which said drive circuit meanscomprises a first drive circuit connected to said first servomotor, afirst pair of AND gates connected to said first drive circuit and saidfirst-named gate for controlling flow of said pulses from saidfirst-named gate to said first drive circuit to select a rotationaldirection of said first servomotor in accordance with said numericalinformation, a second drive circuit connected to said second servomotor,and a second pair of AND gates connected to said second servomotor andsaid first-named gate for controlling flow of said pulses from saidfirst-named gate to said second drive circuit to select a rotAtionaldirection of said second servomotor, whereby said first and secondservomotors may be simultaneously rotated in the same direction.
 6. Agrinding machine comprising a bed, a wheel slide slidably mounted onsaid bed, a grinding wheel rotatably supported on said wheel slide, atable mounted on said bed operably to support a workpiece, a feed screwmovably mounted on said bed and threadedly engaging with said wheelslide to move same, feed means drivingly engaging with said feed screw,a first pulse motor mounted on said wheel slide, a worm secured to theoutput shaft of said first pulse motor, a nut member rotatably mountedon said wheel slide and engaging with said feed screw, a worm wheelcoaxially secured to said nut member and engaging with said worm, asizing head mounting two vertical guide bars fixedly secured thereto attheir upper and lower ends, a second pulse motor mounted on said sizinghead, a threaded rod rotatably mounted on said sizing head in parallelrelation to said guide bars and drivingly engaged with said second pulsemotor, a pair of feelers slidably mounted on said guide bars anddrivingly engaged with said threaded rod, said pair of feelers beingmaintained in contact with said workpiece at positions on said workpiecediametrically opposed to each other during a grinding operation, adetector mounted on one of said feelers for providing a sizing signal tocontrol said feed means during said grinding operation, a first drivecircuit connected to said first pulse motor to drive the same, a firstpair of AND gates connected to said first drive circuit for controllingflow of pulses into said first drive circuit to select a rotationaldirection of said first pulse motor in accordance with numericalinformation, a second drive circuit connected to said second pulse motorto drive the same, a second pair of AND gates connected to said seconddrive circuit for controlling flow of pulses into said second drivecircuit to select a rotational direction of said second pulse motor inaccordance with said numerical information, a gate connected to saidfirst and second pair of AND gates and permitting a predetermined numberof pulses corresponding to numerical information to pass therethrough,said numerical information corresponding to the differential in adesired finish diameter between said workpiece and a workpiecepreviously worked, and pulse generator means providing a train of pulsesto said first and second pair of AND gates through said last-named gate,whereby said first and second pulse motors may be simultaneously rotatedin accordance with said numerical information.